Methods are known in the art of glass manufacturing for preheating glass batch wherein glass-forming, batch ingredients are brought in direct contact with heated media within a chamber. The particulate or granular glass batch raw materials are brought in particle-particle heat exchange with media that has been heated with an external burner or heated by direct contact with exhaust gases from a glass melting furnace. This method allows the exchange of large quantities of heat economically and uniformly.
Before remelting scrap glass, organic binders and sizes on the surface of the glass must be removed. If this is not done, the glass will enclose the remaining binder in the form of carbon. Upon melting, carbon will reduce the glass. This reduced darkened glass is undesirable for both glass composition and melting.
One method of doing this is to mill the scrap glass and blend it with granular raw batch before charging the batch to the furnace. It is important to ensure that oxidizing conditions are maintained in the glass melt within the furnace so that the glass furnace may feed a fiberizing process without harmful effects.
This process has many inherent disadvantages. For example, the scrap glass must be passed through a shredding operation and stored in a silo before blending with conventional granular batch. Further, the process demands that an entire glass furnace be kept at oxidizing conditions to ensure that carbonaceous material is removed.